Mixing Tank Research Articles

Efficient adsorption of antibiotics using MXene nanosheet delaminated by Taylor vortex flow

MXenes are emerging as a promising class of two-dimensional (2D) adsorbents suitable for various environmental applications. The present study explores the use of Ti3C2Tx MXene nanosheet, delaminated by Taylor vortex flow (TVF), namely d-MXene-CT, as an efficient adsorbent for fluoroquinolones (FQs). The TVF induced in the gap between two coaxial cylinders of the Couette-Taylor reactor enhances the delamination process, yielding larger and thinner MXene nanosheets with a specific surface area 12 fold higher than that of nanosheets delaminated by turbulent eddy flow (TEF), namely d-MXene-MT in a conventional mixing tank (MT) reactor. As a result, the d-MXene-CT exhibited superior adsorption performance, with removal capacity for ciprofloxacin (CIP) of 349 mg/g and for levofloxacin (LEV) of 290.51 mg/g, representing 40 ∼ 60 % improvement over d-MXene-MT (249 mg/g for CIP and 180.22 mg/g for LEV). The adsorption process follows the pseudo-second-order kinetics model and fits the Langmuir isotherm, indicating the involvement of a monolayer chemisorption mechanism. Further investigation revealed that the removal of CIP and LEV was mainly driven by electrostatic attraction between oxygen functionality of MXene and protonated nitrogen group of FQs. The study highlights the potential of d-MXene-CT as a promising adsorbent for treating (FQs) from contaminant water.

Production of Monodisperse Large Drop Emulsions by Means of High Internal Phase Pickering Emulsions-Processing and Formulation.

High internal phase Pickering emulsions (HIPPE) have received significant research attention in the last two decades due to their potential for a wide range of applications. The appropriate processing of such high-viscosity emulsions, hundreds of times more viscous than that of the continuous phase, and the control of the final droplet size remain challenges to be tackled. Our research targeted this knowledge gap by examining the influence of the emulsion formulation and the processing conditions on the final droplet size. The dispersed phase fraction (100 cSt silicon oil) ranged between 75 and 80%. The emulsions were produced in a regular mixing tank equipped with a helical ribbon impeller rotating at a low speed (100-150 rpm). The effective viscosity of the continuous phase was obtained from the experimental torque measurements. The droplet size distributions were measured after emulsification and dilution in the continuous phases. It is shown that the capillary number obtained from the observed emulsification performance can help predict the final droplet size. Our approach provides a straightforward methodology to generate concentrated Pickering emulsions with controlled and predictable droplet size.

Research on adaptive hydraulic drive optimization control of concrete mixing tank truck for open-pit mine.

The non-axisymmetric problem caused by the fluid sloshing in the tank of a mining concrete mixing tank truck during driving is affected by the excitation of complex road surfaces. The fluid sloshing is coupled with the dynamics of the vehicle body due to the excitation of the complex road surface. The traditional hydraulic drive proportional integral differential (PID) control method is not effective in dealing with such problems, which can easily lead to accidents such as overturning. To improve the accuracy and stability of the hydraulic drive control system, this paper proposes an optimized particle filter PID adaptive control method based on the elastic firefly (FA) algorithm to accelerate the convergence speed of control parameter optimization, and then analyzes its hydraulic drive control characteristics and structural applications, and discusses step steering and double lane change modes are simulated under filling rates of 1.5 and 2.0, respectively. The experimental results show that compared with traditional PID control, the proposed adaptive control method can significantly reduce the average speed error of hydraulic drive control to 0.03km/h and the maximum speed error to 0.17km/h. It also improves the control tracking performance and stability. The practicality of the adaptive hydraulic drive is verified in the filling rate experiments under step steering and double-lane shifting conditions. It has important reference value for the practical application of hydraulic drive control optimization of mining concrete mixing transport tank trucks.

Coarse bubble mixing in anoxic zone greatly stimulates nitrous oxide emissions from biological nitrogen removal process

The biological nitrogen removal process in wastewater treatment inevitably produces nitrous oxide (N2O), a potent greenhouse gas. Coarse bubble mixing is widely employed in wastewater treatment processes to mix anoxic tanks; however, its impacts on N2O emissions are rarely reported. This study investigates the effects of coarse bubble mixing on N2O emissions in a pilot-scale mainstream nitrite shunt reactor over a 50-day steady-state period. Online and offline N2O monitoring campaigns show that coarse bubble mixing in the anoxic zones significantly elevates N2O emissions, yielding an extremely high emission factor of 15.5 ± 3.5 %. Intensive sampling and isotopic analyses suggest that the elevated emissions are primarily due to the inhibition of the N2O denitrification process by oxygen in the anoxic phase introduced by coarse bubbling. Substituting coarse bubble mixing with submersible pump mixing resulted in a substantial reduction of N2O emissions, decreasing the emission factor by an order of magnitude to 1.2 ± 0.8 %. The findings reveal that a previously overlooked factor, coarse bubble mixing, can significantly stimulate N2O emissions. The use of coarse bubble mixing in anoxic tanks of biological nitrogen removal warrants caution.

Using CFD and machine learning to explore chaotic mixing in laminar diameter-transformed stirred tanks

Elimination of segregated zones is important to intensify the global chaotic mixing of high-viscosity fluids. Diameter-transformed stirred tank (DTST) reactor as a new process-intensification equipment is proposed. Through the PLIF technique, tracer transport CFD modeling, and Poincaré sections, we investigate the mixing structures inside a DTST reactor, and find that the DTST reactor can trigger global chaotic mixing. This is due to the wall squeezing effect, causing the fluid particle in periodic motion to become disordered. From the perspective of mixing kinetics, an area coverage model A=Amax1-e-Eamt is developed to quantitatively characterize its mixing efficiency, and the maximum area coverage Amax is 98.12 %. In addition, to help practitioners quickly select a suitable DTST reactor under different working conditions, machine learning-based flow pattern prediction models are proposed, among the ANNc model has a highest accuracy of 97.6 %. The decision boundary can be expressed by the Rec-E discriminant lg(Rec)=2.3(E-0.95)0.18-1.

An Algorithm for Nutrient Mixing Optimization in Aquaponics

Controlled environment agriculture is a promising alternative to conventional production methods, as it is less affected by climate change and is often more sustainable, especially in circular and recycling frameworks such as aquaponics. A major cost factor in such facilities, however, is the need for skilled labor. Depending on available resources, there are endless possibilities on how to choose ingredients to realize a desired nutrient solution. At the same time, the composition of the desired solution is subject to fluctuations in fish water quality, fertilizer availability, weather, and plant development. In high-evaporation scenarios, e.g., summer, nutrient solutions might be mixed multiple times per day. This results in a complex, multi-variable task that is time-consuming to solve manually, yet requires frequent resolution. This work aims to help solve this challenge by providing methods to automate the nutrient mixing procedure. A simple mass-balance-based model of a nutrient mixing tank with connections to different water sources, drains, and fertilizers is provided. Using methods of static optimization, a program was developed which, in consideration of various process constraints and optimization variables, is able to calculate the necessary steps to mix the desired solution. The program code is provided in an open-source repository. The flexibility of the method is demonstrated in simulation scenarios. The program is easy to use and to adapt, and all necessary steps are explained in this paper. This work contributes to a higher automation level in CEA.

Dynamic tank-in-series modelling and simulation of gas-liquid interaction in trickle bed reactor designed for gas fermentation

Trickle bed reactors (TBR), historically utilized in petroleum processing and wastewater treatment, now extend their applicability in biological gas conversions, including syngas biomethanation for renewable methane production. Despite operational benefits, optimizing TBR design and scale-up demands a good understanding of the reactor's hydraulic behavior and mass transfer phenomena. This study's novelty is TBR's hydraulic characterization in respect to liquid and gas flowrates and simulation of the gas-liquid interaction by a dynamic gas-liquid transfer model. Residence time distribution (RTD) experiments in 220 mL lab- and 5000 mL pilot-scale TBRs with co-current flow of gas and liquid were conducted to determine the liquid and gas working volume and the number of tanks for a dynamic tank-in-series (TIS) model. RTD experiments revealed 2–6 tanks for varying liquid flowrate (constant gas flowrate) and 5–8 tanks for varying gas flowrate (constant liquid flowrate). A dimensionless equation, fitted to RTD experimental data, predicted the liquid working volume of a TBR at various liquid flowrates and reactor configurations. TBR simulation by TIS model considering 8 well mixed gas and liquid phase tanks connected in series, resulted in an excellent model validation with an R2 at 0.99. Finally, the model simulated the mass transfer kinetics of H2, CO, and CO2 in water under varying gas and liquid flowrates for lab- and pilot-scale TBRs. Simulation results showed increased dissolved gas concentration with higher gas flowrate (constant liquid flowrate) for both scales TBR. It was also noticeable that under constant gas flowrate, the dissolved gas concentration initially decreased (0.01 < ReL < 17), then increased (17 < ReL < 34), and again decreased (34 < ReL < 105). This behavior was the same for both scales TBR and revealed an optimum ReL value irrespective of TBR size.

Optimising the hygiene of a liquid feeding system to improve the quality of liquid feed for pigs

Poor feeding system hygiene may contribute to uncontrolled spontaneous fermentation in liquid pig feed and its associated undesirable effects. This study aimed to determine the effects of an intensive sanitisation programme in a grow-finisher liquid feeding system by monitoring microbiological and physico-chemical parameters of liquid feed and microbial colonisation of the feeding system surfaces. The sanitisation programme involved a combination of physical and chemical cleaning between batches of grow-finisher pigs, combined with nightly rinsing of the system with an organic acid blend. Improved hygiene of the internal surfaces of the mixing tank and feed pipeline, particularly until week 5 post-cleaning, was evidenced by reduced counts of lactic acid bacteria, total aerobes, Enterobacteriaceae, yeasts and moulds and decreased adenosine triphosphate concentrations. Enterobacteriaceae and moulds remained undetectable on pipeline surfaces for 10 weeks. Scanning electron microscopy of the feed pipelines confirmed these findings. Conversely, the impact on liquid feed microbiology was minimal and short-lived. However, acetic acid, ethanol and biogenic amine concentrations decreased in the feed post-cleaning and no gross energy losses were observed. Therefore, by controlling surface microbial communities on liquid feeding systems via implementation of the sanitisation programme developed in the current study, on-farm liquid feed quality should be improved.

Deracemization of sodium chlorate by hydrodynamic attrition of Taylor vortex flow

We investigated the deracemization of sodium chlorate in the unique hydrodynamic environment of Taylor vortex flow (TVF) in Couette-Taylor (CT) crystallizer. Our findings revealed a remarkable enhancement in the deracemization due to the effective hydrodynamic attrition of crystals, as compared to conventional mixing tank (MT) crystallizers utilizing the turbulent eddy flow (TEF). So, the deracemization of initial ee = 0 % in the CT crystallizer was significantly enhanced as increasing the rotation speed whereas the deracemization in the MT crystallizer occurred seldom with increase of agitation speed. Using the sparsely soluble solvent, it was demonstrated the TVF was much more effective for the hydrodynamic attrition of the crystals than the TEF. The deracemization depended not only on the flow intensity (viscous energy dissipation) but also the flow pattern. So, the TVF always produced the higher deracemization than the TEF at the same viscous energy dissipation. Also, the flow intensity and flow pattern significantly dictated the crystal agglomeration of homo-chiral (L-form and D-form) and hetero-chiral (L/D-form) forms during the deracemization. Our findings demonstrated the potential of the periodic TVF in the deracemization. The hydrodynamic attrition effect in the CT crystallizer provides a means to enhance enantiomeric purity and offers insights into the design of novel deracemization systems.

Biogas production performance using soybean residue and hydrothermal pretreated food waste hydrolysate in a continuously anaerobic two-stage pilot plant

In this study, a continuously anaerobic two-stage pilot plant was established for bioenergy production, comprising 5 major pieces of equipment: a mixing tank, 1st anaerobic digester (AD), 2nd AD, sediment tank, aeration tank, and final sediment tank, all operating at ambient conditions. The operation of the continuously anaerobic two-stage pilot plant was automatically controlled by a programmable logic controller (PLC) using a designed control logic concept to set the hydraulic retention time (HRT) and inlet substrate concentration. The organic loading rate, pretreatment of hydrolysis pressure, and microbial community analysis were investigated for their effects on biogas production performance using different substrates: soybean residue (SR) and food waste hydrolysate (FWH), respectively. It was found that the peaks of biogas production rate on daily volumetric feeding were 1.20 m³·m⁻³·d⁻1, and the biogas yield on VS added was 760 dm³·kg⁻1 from food waste hydrolysate with a pretreatment hydrolysis pressure of 10 kg cm⁻2, at an OLR in COD concentration of 3.56 kg m⁻³·d⁻1, and an HRT of 11 days, respectively. The Methanobrevibacter genus was found to be abundant in the 1st AD, approximately 6.7 times more abundant than in the 2nd AD. The continuous anaerobic two-stage pilot plant was properly examined for its application in treating food waste and soybean residue with the goal of obtaining renewable bioenergy.

Numerical and experimental approach for dust dispersion and deposition behavior for safe decommissioning activities

ABSTRACT The use of high-fidelity modeling is a promising technique for studying the mechanisms of dust dispersion and deposition in safe decommissioning operations. Detailed multiphysics models for poly-dispersed turbulent flow, particle-laden flow, and particle surface interaction were coupled with a Reynolds Averaged Navier Stokes method for numerical simulation of dust dispersion and deposition. A model that considered the critical viscosity was utilized to estimate the interaction between particles and substrate. The deposition behavior of particles was a result of the competition between adhesion and rebound probabilities during the impact process, and only when the critical viscosity exceeded that of the impacting particles could they attach to the surfaces. To validate the accuracy of the simulation results, deposition experiments using zirconia particles were conducted. The experimental setup included a 3.2 m polycarbonate pipe, a fan regulated by an inverter to control the flow, an ultra-low penetration air filter capable of capturing particles with a minimum diameter of 120 nanometers. An air pump connected to a particle tank and a mixing tank was used for homogenizing the injection of particles. Particle concentration was measured during the experiments using a light scattering spectrometer system, WELASⓇ 2000, from the manufacturer PalasⓇ. This optical measurement technique functioned with a white light source and scattered light detection. The scattered light was collected via optical fibers, which led to the control and evaluation point, and results were displayed through special software. The numerical simulation results were compared with the experimental data and used to validate the numerical approach for flow with zirconia particles deposited on various material surfaces, including iron, titanium, stainless steel 304, and stainless steel 316, for airflow rates ranging from 54 L/min to 124 L/min.

Ship system design changes for the transition to hydrogen carriers

Reducing the use of fossil fuels in shipping requires new, alternative maritime fuels. Hydrogen carriers offer a safe and energy-dense solution for storing hydrogen, a zero-emission alternative fuel. This research focuses on ammonia borane, NaBH4, n-ethylcarbazole and dibenzyltoluene. Applying hydrogen carriers influences ship design significantly, as they require additional specialised equipment to remove hydrogen from the hydrogen carrier. This research estimates the size of the equipment. As this equipment will needto be stored and maintained on the ship, the exact sizing and sequence of the additional equipment will likely influence ship design. Results show that the reactor size is significant for all hydrogen carriers. The mixing tank is considerably sized for NaBH4 and ammonia borane, while the heat exchangers are large for dibenzyltoluene and n-ethylcarbazole.

Experiment-supported survey of inefficient electrolyte mixing and capacity loss in vanadium flow battery tanks

This study investigates the impact of electrolyte mixing inside the tanks of Vanadium Flow Battery (VFB) on capacity degradation. Heterogeneous mixing inside the tanks may lead to a severe capacity drop due to the existence of stagnant electrolyte regions and asymmetries in the State of Charge (SoC) of the positive and negative electrolytes reaching the cell. The study is based on a preliminary order-of-magnitude analysis involving the dimensionless Richardson and Reynolds numbers. A subsequent experimental campaign is carried out in which cell voltage and current response are screened for different tank designs and operating conditions to identify different fluid-dynamics events in the tanks. The results highlight the two main competing phenomena affecting the electrolyte fluid dynamics: buoyancy effects induced by density variations, and the inertia of the inlet submerged jet. The interplay between these two forces determines the flow field and therefore the SoC of the electrolyte feed to the cell, which affects the usable capacity and battery performance. Inertia dominated flows induce homogeneous electrolyte mixing, leading to a higher usable capacity, whereas buoyancy dominated flows result in a lower one. Furthermore, various inner structures were tested within the tanks to optimize mixing. These structures were created using additive manufacturing techniques. The implementation of helicoidal geometries within the tanks, promoting longer electrolyte paths and ample cross-sectional areas for convective mixing, markedly enhanced battery capacity compared to traditional empty tanks. These findings call for further investigation into optimizing the geometry of large-scale (VFB) storage tanks.

Intensive Microalgal Cultivation and Tertiary Phosphorus Recovery from Wastewaters via the EcoRecover Process.

Mixed community microalgal wastewater treatment technologies have the potential to advance the limits of technology for biological nutrient recovery while producing a renewable carbon feedstock, but a deeper understanding of their performance is required for system optimization and control. In this study, we characterized the performance of a 568 m3·day-1 Clearas EcoRecover system for tertiary phosphorus removal (and recovery as biomass) at an operating water resource recovery facility (WRRF). The process consists of a (dark) mix tank, photobioreactors (PBRs), and a membrane tank with ultrafiltration membranes for the separation of hydraulic and solids residence times. Through continuous online monitoring, long-term on-site monitoring, and on-site batch experiments, we demonstrate (i) the importance of carbohydrate storage in PBRs to support phosphorus uptake under dark conditions in the mix tank and (ii) the potential for polyphosphate accumulation in the mixed algal communities. Over a 3-month winter period with limited outside influences (e.g., no major upstream process changes), the effluent total phosphorus (TP) concentration was 0.03 ± 0.03 mg-P·L-1 (0.01 ± 0.02 mg-P·L-1 orthophosphate). Core microbial community taxa included Chlorella spp., Scenedesmus spp., and Monoraphidium spp., and key indicators of stable performance included near-neutral pH, sufficient alkalinity, and a diel rhythm in dissolved oxygen.

A Novel Experimental Apparatus for Characterizing Flow Regime in Mechanically Stirred Tanks through Force Sensors.

Pressure fluctuations in a mixing tank can provide valuable information about the existing flow regime within the tank, which in turn influences the degree of mixing that can be achieved. In the present work, we propose a prototype for identifying the flow regime in mechanically stirred tanks equipped with four vertical baffles through the characterization of pressure fluctuations. Our innovative proposal is based on force sensors strategically placed in the baffles of the mixing tank. The signals coming from the sensors are transmitted to an electronic module based on an Arduino UNO development board. In the electronic module, the pressure signals are conditioned, amplified and sent via Bluetooth to a computer. In the computer, the signals can be plotted or stored in an Excel file. In addition, the proposed system includes a moving average filtering and a hierarchical bottom-up clustering analysis that can determine the real-time flow regime (i.e., the Reynolds number, Re) in which the tank was operated during the mixing process. Finally, to demonstrate the versatility of the proposed prototype, experiments were conducted to identify the Reynolds number for different flow regimes (static, laminar, transition and turbulent), i.e., 0≤Re≤ 42,955. Obtained results were in agreement with the prevailing consensus on the onset and developed from different flow regimes in mechanically stirred tanks.

Fuzzy-Based Control System of Drilling Fluids Density and Apparent Viscosity Simultaneously: An Alternative Strategy to Support Autonomous Drilling Operations

Summary Among all the systems that make up a drilling operation, the production and correction of drilling fluid can be considered the heart of the process. Among the main objectives of the drilling fluid are to cool the drill bit and maintain the pressure gradient inside the drilling well, which is done by controlling its density. Another important function is transporting the cuttings from the bottom to the surface and keeping them in suspension in case of stoppage, which directly depends on the viscosity of the drilling fluid. Density and viscosity must be constantly maintained within an operational window, and failures can lead to serious accidents, even the loss of the well. Currently, this control is done manually: An operator collects samples of the fluid and takes them for analysis in the laboratory and subsequently makes the necessary corrections by manually adding products to the fluid. To reduce process dead time, keep personnel on board, and increase operation safety, a control and monitoring system is necessary. Fuzzy logic was chosen because it can be combined with classical methods, is cheap to develop and implement, and can be customized in terms of natural language, capturing the knowledge acquired by operators from equipment operation, bench tests, etc. This work aimed to develop a novel real-time monitoring and fuzzy-based system for simultaneous control of the apparent viscosity and density of non-Newtonian fluids, dealing with the inevitable interactions between them in a pilot experimental unit. A pilot plant was built to evaluate the fuzzy system approach for modeling and controlling of density and apparent viscosity of drilling fluids. The pilot flow loop comprises a mixing tank, solids vibrating feeders, and a water-dosing pump. The unit was instrumented with online sensors to measure fluid density, temperature, flow rate, differential pressure, and viscosity. The apparent viscosity and density of the non-Newtonian fluid were controlled by manipulating the dosage of carboxymethylcellulose (CMC), barite, and water. The proposed methodology was compared to a classical proportional-integral-derivative (PID) controller in servo and regulatory scenarios for apparent viscosity and density. The results showed that the fuzzy controller dealt adequately with the effect of variable interactions, keeping both variables within their setpoint ranges, demonstrating the ability to control them individually despite their interactions. These results also showed that the fuzzy-based controller could easily be integrated into a diagnostic-predictive monitoring system to control fluid properties, accomplishing setpoint changes and rejecting undesirable disturbances presenting a maximum overshoot of 7.5% for apparent viscosity and 0.3% for density.

Self-powered wireless flexible sensing for food storage based on triboelectric-electromagnetic generator

In Controlled Atmosphere (CA) food storage, maintaining optimal conditions, including gas concentration, temperature, and humidity on the food surface, is crucial. This paper proposes the application of a self-powered wireless flexible sensing system based on a triboelectric-electromagnetic generator in food CA storage. To configure certain concentrations of mixed CA gases, we need to accurately control the volume of CA gas input into the mixed gas tank within a certain period, and the gas flow velocity in the pipeline will directly affect this factor. The gas flow velocity in the pipeline is detected by the CA gas flow velocity detection part (FVS) with an independent layer working mode triboelectric nanogenerator (FV-TENG) as the main component. Simultaneously, a flexible Temperature and Humidity Sensor (THS) affixed to the food surface provides real-time monitoring. EMG collects irregular wind energy in the CA warehouse to provide energy for the processing of information in the system and wireless transmission to the IoT cloud platform, realizing the system's self-power and wireless transmission. The self-powered wireless sensing system facilitates remote collection of CA gas flow velocity data, precise control of mixed atmosphere gas concentrations, and real-time monitoring of food surface temperature and humidity in the CA warehouse.

ELECTROCOAGULATION SYSTEM FOR TREATMENT OF BALLAST WATER

This study aimed to determine the removal of hazardous materials in ballast water by using an electrocoagulation (EC) system. This research was carried out on January 16 – June 15 2023 in Batam City. Ballast water was supplied by tanker ships anchored at 5 ports in Batam Island, namely Batam Centre, Sekupang, Nongsapura, Telaga Punggur, and Batu Ampar. The ballast water was collected and processed through an electrocoagulation system at PT. Batam Air Cargo Village, Batam. Meanwhile, the quality of the treated ballast water was examined by PT. Mutuagung Lestari Batam, Batam, Indonesia. If the laboratory test results meet the requirements, then the remaining ballast water can be disposed of into nature. However, if the test results are not met, then the ballast water is re-processed and channeled to the mixing tank. The physical parameters of the treated ballast water showed a temperature of 28oC, total dissolved solids (TDS), and total suspended solids (TSS) of around 140 and 11 mg/L respectively. The main heavy metal content of ballast water after the electrocoagulation process showed cadmium (&lt; 0.001 mg/L), chrome (&lt; 0.02 mg/L), mercury (&lt; 0.0001 mg/L), lead (&lt; 0.005 mg/L), copper (0.14 mg /L), zinc (0.31 mg/L), and arsenic (&lt; 0.0001 mg/L). The physical parameters of the treated ballast water showed a temperature of 28oC, total dissolved solids (TDS), and total suspended solids (TSS) of around 140 and 11 mg/L respectively. The main heavy metal content of ballast water after the electrocoagulation process showed cadmium (&lt; 0.001 mg/L), chrome (&lt; 0.02 mg/L), mercury (&lt; 0.0001 mg/L), lead (&lt; 0.005 mg/L), copper (0.14 mg /L), zinc (0.31 mg/L), and arsenic (&lt; 0.0001 mg/L). Other chemical and biological parameters that were also measured included sulfide (&lt; 0.002 mg/L), fluoride (0.11 mg/L), chlorine (0.05 mg/L), ammonia (0.78 mg/L), nitrate (&lt; 0.05 mg/L), nitrite (&lt; 0.004 mg/L), total nitrogen (0.78 mg/L), BOD5 (22.69 mg/L), methylene blue active compound (0.732 mg/L), phenol (0.001 mg/L), oil and fat (1.032 mg/L), pH (7.13), and total coliform (615 MPN/100). All parameters showed that the hazardous content of electrocoagulated ballast water waste has met the quality standards for ballast water waste. It has also been tested to process other liquid waste. So, it is very promising to be developed for other waste processing needs in the future.

Fluid–Solid Mixing Transfer Mechanism and Flow Patterns of the Double-Layered Impeller Stirring Tank by the CFD-DEM Method

The optimization design of the double-layered material tank is essential to improve the material mixing efficiency and quality in chemical engineering and lithium battery production. The draft tube structure and double-layered impellers affect the flow patterns of the fluid–solid transfer process, and its flow pattern recognition faces significant challenges. This paper presents a fluid–solid mixing transfer modeling method using the CFD-DEM coupling solution method to analyze flow pattern evolution regularities. A porous-based interphase coupling technology solved the interphase force and could be used to acquire accurate particle motion trajectories. The effect mechanism of fluid–solid transfer courses in the double-layered mixing tank with a draft tube can be obtained by analyzing key features, including velocity distribution, circulation flows, power, and particle characteristics. The research results illustrate that the draft tube structure creates two major circulations in the mixing transfer process and changes particle and vortex flow patterns. The circulating motion of the double-layered impellers strengthens the overall fluid circulation, enhances the overall mixing efficiency of the fluid medium, and reduces particle deposition. Numerical results can offer technical guidance for the chemical extraction course and lithium battery slurry mixing.

Preconcentration of a Medium-Grade Celestine Ore by Dense Medium Cyclone Using a Factorial Design

A semi-industrial scale hydrocyclone with a 250 mm internal diameter was used to concentrate medium-grade celestine ore (75%–85% celestine) from the Montevive deposit of Granada (Spain) using a dense ferrosilicon (FeSi) medium. For this purpose, a Box–Behnken factorial design (BBD) was carried out, with the response variable being the Sr concentration measured by X-ray fluorescence (XRF), as well as the concentration of celestine measured by X-ray diffraction (XRD) of the mineral collected from the under (sunk) stream of the hydrocyclone. The experimental factors to be optimised were the density of the medium in the mixing tank (water, FeSi, and feed mineral) varying from 2.7 to 2.9 kg/L, the hydrocyclone inlet pressure from 0.8 to 1.2 bar, and the hydrocyclone inclination (from 15° to 25° from the horizontal). The range of densities of the dense medium to be tested was determined from previous sink–float experiments using medium-grade ore, in which the distribution of mineral phases with different particle size fractions was determined. To evaluate the separation behaviour, the following parameters were considered: the enrichment ratio (E), the tailings discarding ratio (R), and the mineral processing recovery (ε). From the factorial design and the response surface, the optimum parameters maximising celestine concentration in the under stream (78%), were determined. These optimised parameters were: a density of 2.75 kg/L for the dense medium, an inlet pressure of 1.05 bar, and a hydrocyclone inclination varying from 18° to 20°. Under these conditions, a 94% recovery of celestine (68% Sr) can be achieved. These results show that medium-grade celestine ore, accumulated in mine tailings dumps, can be effectively concentrated using DMS hydrocyclones and that the operating parameters can be optimised using a factorial experiment design. This study can contribute to reducing overexploitation of strategic mineral resources, avoiding blasting and environmentally damaging clearing, by applying a simple and sustainable technique.